Core G: Imaging Radiation Pathology Studying the downstream effects of radiation or the efficacy of therapeutic intervention fundamentally depend on visualization and quantitation of effect. These are commonly best assessed using quantiativie microscopic approaches. The Imaging Radiation Pathology Core is housed within the Center for Biologic Imaging, in which this core service will be performed, is designed for the purpose of providing state of the art microscopic technologies to its users. It is equipped to perform a continuum of optical methods including all types of light and electron microscopy essential to this Program. All investigators have made, and continue to make, heavy use of the CBI for facility-specific imaging methodologies. Evidence of the longevity of this use is seen in co-authored publications between the PI and staff of the Core (Watkins, St. Croix, Stolz) and PI's of the individual projects. The imaging specialties afforded by CBI include all ultrastructural electron microscopy (transmission electron microscopy, scanning electron microscopy, immuno-electron SEM and TEM), light and fluorescence microscopy (macro dissecting light and fluorescence, epi-fluorescence, confocal scanning and multi-photon imaging), live cell microscopy (transmitted light and fluorescence) and fluorescence specialties like FRET, FRAP spectral analysis and ratiometric imaging. Also critical to data processing, a wide range of image analysis software and technical assistance is available to program investigators.